Control mechanism



3 947. G. T. HART, JR

I common mscmmsm Filed Oct. 28, 1942 Patented July 15, 1947 CONTROL MECHANISM George T. Hart, Jr., Lynn, Masa, assignor to United Shoe Machinery Corporation, Flemington, N. J., a corporation of New Jersey Application October 28, 1942, Serial No. 463,679

13 Claims.

This invention relates to control mechanisms, and more particularly to mechanisms for controlling th operation of a motor to determine the direction and extent of movement of a movable contrivance or member. An object of the present invention is to provide an improved control mechanism of the above-mentioned type by means of which a smoother operation of the motor is effected with resultant greater ease and accuracy of control. It will be understood, however, that the invention in its various novel and useful aspects is not limited to use in control mechanisms of the particular type illustrated.

For the purpose in view, and in accordance with one feature of the invention, there is provided a pulsating device for controlling the operation of a motor whereby a series of automatically repeated pressure impulses are imparted to the motor as the usual control member, with which control mechanisms of the above-mentioned type are provided, is moved to start the motor in operation. Not only is the operation of the motor thus rendered smoother, but a mor sensitive control of its operation and of the extent of movement of the work piece is provided, since any tendency for friction between the parts to delay the action of the motor in' response to movements of the control member is avoided.

In the illustrated arrangement, an electromagnetic device, to which a pulsating current is supplied, operates a valve of a fluid-pressure system to draw it away from the original neutral, or closed, position and as rapidly to return it to that original position. When this is done at a high frequency, a series of small impulses are imparted to the motor, thereby advantageously starting the motor gradually and at the same time providing a system in which the impulses can be rapidly withdrawn so that there shall be no overrunning of the motor.

In accordance with still another feature of the invention, there is provided an arrangement in which a vibratory force is imparted to a control device so that it is rapidly vibrated. or dithered, and in which this vibratory force is superimposed on a steady force imparted to the control in the same direction, for example, as the pulsating force. This may advantageously be accomplished, as herein illustrated, by also including in the control system a solenoid-operated-valve mechanism which is restrained, or delayed, as by means of a dashpot. I

These and other features of the invention will best be understood from a consideration of the following specification taken in connection with the accompanying drawing, in which Fig. 1 is a diagram illustrating the control system of the present invention applied to the training of a gu Fig. 2 is an enlarged detail, in horizontal secturning a vibrating and Fig. 4 is a side elevation of these parts, taken from the left in Fig. 1, and with portions in section.

The control system is herein illustrated as cyclically operated and utilized for training a gun in elevation by means of signals received from a remote-control device, such as a telescope or sight.

A manual movement of the telescope is followed by a corresponding movement of the gun, thus completing one cycle. It will be understood, however, that this is only one application of the system which can be utilized wherever it is desired to move a member, such as a gun, a'deflnite amount under the control of an operator who may be near or far away. A gun III is herein shown as capable of tilting with ahorizontal axle l2 to change its elevation in responseto signals from a similarly tiltable telescope or sight" l4. Carried on the axle l2, iortilting movement with the gun, is a pair of contacts l6, l8 associated with which is an intermediate contact 20 operator-controlled by connection to the sight I4 as by means of a Selsyn generator or transmitter 22 and a receiver 24 shown as connected to a source of alternating-current power such as the mains 26. To this end,the rotor 28 oi! the transmitter 22 is gear-connected to a segment 30 on the sight l4, while the rotor 32 of the receiver 24 is geared to a segment 34 carrying the intermediate contact 20.

Tilting movement to elevate or depress the gun is imparted to the axle l2 and hence to the gun by means of a fluid-pressure motor 40 the piston of which is connected to a, rack 42 meshing with a segment 44 upon said axle. The hydraulic m0- tor to is controlled by a piston-type slide valve unit 46. This is normally in a neutral, or closed, position, as shown in Fig. l, in which pressure fluid supplied through the pipe 48 cannot be delivered to either of th pipes 50, 52 leading to opposite sides of the piston of the motor 40. When a slight movement in one direction or the other is imparted to the valve piston 54 of the unit 46, pressure fluid is admitted to one end of the motor and is exhausted through one of the ports 56 from the other end of the motor.

Movements of the valve are effected by impulses transmitted to the valve piston 54 by means of a lever 60 connected to said valve piston by a link 62. This lever is supported and fulcrumed at 64 on a fulcrum block 66 carried by a rod 68 slidably guided in fixed supports 10. At

its other end, the lever 80 is Iulcrumed at 12 to a rigid rod 14 which is connected to a lever 18 of an armature 18 adapted to be tilted about a fixed axis 19 in one direction or the other by electromagnets 80, 82. e dual means provided by these magnets are eflective to cause recurrent movements of the control valve each in a different direction away from its neutral closed position, thereby intermittently to open the valve slightly. After each such movement, the valve is urged toward its neutral position by a spring centering device 15 for returning this armature lever 18 to its mid position. This device is supported between fixed members 84 and comprises, as shown specifically in Fig. 2, a rod 88 having an enlarged block-like abutment 88. This rod is supported in the fixed members 84 by screws 80, '92 having reduced portions surrounded by coil springs 94, 98, respectively, which bear at their inner ends upon headed sleeves 88, I00, the springs 84, 88 acting to hold the headed sleeves against opposite sides of the enlarged abutment 88. The armature lever 18 has a forked upper end the arms 11 of which bear disk-like rolls I02 each having a diameter which is equal to the distance between the ends of the abutment 88. The result of this arrangement is that exact balancing of the springs is unnecessary and the displacement of the armature lever 18 in either direction is opposed by one of the return springs 94, 88, but only one. A similar centering device I04 carried by the supports 10 acts upon the lower end I08 of the lever 80. This centering device I04 includes a central abutment I88 on a rod which is carried by holders I80 on the supports 10. Pressed against this abutment by springs I84 and I98 are headed sleeves I98 and 200, these numerals being digits made up from those in Fig. 2 by adding 100 and referring to corresponding parts. the fulcrum 84 is effected by solenoids I08, IIO having cores attached respectively to the opposite ends of the rod 88. The action of either one of these solenoids is opposed and rendered gradual by a one-way dashpot, such as that shown at I I2, which is connected to a bell-crank lever II4 one arm of which at its upper end bears against an end of the fulcrum block 88. A similar dash'pot andbell crank are provided to bear upon the opposite end of the block 88 and the bell cranks are urged thereagainst by means of a strong central spring II8 which draws each bell crank against the block 88 and also against a stop pin such as that at II8.

Provision is made for delivering a pulsating current through leads I20 or I22 and a return wire I24 to one of the electromagnets 80, 82 and to One of the solenoids I08, IIO. A resistance I28 and a condenser I28 in series are bridged across the solenoid I08, and a similar arrangement is provided at I28 for the solenoid IIO. This serves to smooth out the pulsations of current and to cause a, steady pull upon one of the solenoids.

Any suitabl arrangement for providing a pulsating current may be interposed between the contacts I8, I8, 20 and the electromagnetic valveoperating device. Illustrated herein are electronic devices I30 the anodes I50 of which are connected to the leads I20 and I22, respectively. Power is supplied to these tubes, which may be gas-filled Thyratron tubes, such as the type designated by the numeral 884," from the mains 28 through an auto-transformer I32. Bridged across a portion I34 of the secondary of this transformer are the heaters I36 f the tubes,

Displacement of the rod 88 which carries the contacts I8 while the other portion of the secondary is connected through a circuit I38 to potentiometers I40 arranged in a parallel circuit the other end of which is connected to the intermediat operator-controlled contact 20 associated with the gun. The other contacts I8, I8 on th gun are connected to the grids I42 of the respective tubes to which the arm I44 of a corresponding p0- tentiometer is also connected through a suitable resistance I48. The tubes are shown as provided with shield grids I48 between the grid and the anodes I50, and thes shield grids along with the cathodes I52 are connected through a lead I84 to the low-voltage end of the auto-transformer I32. The adjustment of the potentiometers is such that a negative bias is provided for the grids I42. As soon, however, as the operator-controlled contact 20 touches one or the other of the contacts I8, I8, a portion of the corresponding potentiometer will be bridged through the corresponding resistance I48, thereby radically changing the grid bias and bringing the tube to a condition where it will be conductive and will supply a pulsating current to the electromagnetic devices which control the valve.

' In the operation of the device during a single cycle of the control system, movement of the sight I4 will impart a movement in a similar direction and amount to the intermediate contact 20 which will, at the end of the previous operation of the mechanism, have been brought to a point between the spaced contacts I8, I8. This tilting of the sight will therefore close the circuit, through the contact I8 for example, thus changing the grid bias on the upper tube I30 and delivering a pulsating current in one direction to the electromagnet and to the corresponding solenoid I08. As noted above, however, the current delivered to the solenoid will be smoothed out before it reaches it. Inasmuch as the action of the solenoid is resisted by the dashpot II2, the valve piston 54 will first be vibrated rapidly by oscillations of the lever 80 having a range lying in one direction away from an initial or neutral position. These vibrations about the fulcrum 84 are effected by means of one magnet such as that at 80. A series of rapid pulsations will be imparted to the valve to open it a small fraction of the width of an associated part in one direction and as rapidly to close it, thus delivering a series of impulses all in the same direction to one side of the hydraulic motor 40. A gradual and smooth starting of the motor is thus accomplished. It will be understood'that. as the sight is moved, the gun will be moved in the same direction as the sight and to a proportional extent. As th movement of the sight is stopped,

and 20 will be separated as a result of the movement of the gun to the position determined by the sight. The pulsations will then cease and the valve will be immediately returned to its neutral position by the centering device 15 associated with the armature lever 18. In addition, a steady force in the same direction as that imparted by the magnet 80 will be imparted to the valve through the solenoid I08 acting on the fulcrum 84, and this action will-be resisted by the bell crank I I4 attached to the dashpot H2 and by the spring II8 between the two bell cranks. This force will act through the lever 80 to open the valve in the same direction as the pulsations imparted by the electromagnet 80 with which it is concurrent, and it will hasten the response of the hydraulic motor 40 since the forces are additive. J ust as soon,

however, as the ace-aces circuit .is broken between the contacts is and 2B, the solenoid-controlled fulcrum 64 will re turn to its midposition. This will be eilected first by the centering device lot, and this action will then be followed up by the return of the bell crank IM. This bears against one side of the fulcrum block 66. The centering device I04 will be used chiefly for insuring an immediate return of the fulcrum 66 in case there is a delayed action of the bell crank H4 due to imperfect relief of the dashpot.

The action of the pulsating current delivered to one of the magnets 80 or 82 is to set up a series of vibrations having their locus or range in one direction from the central position, that is to say, so that the lever 16 will move either to the left of its central position and back again or to the right of its central position and back again. The frequency of these pulsations is comparatively large, and the degree of movement imparted to the piston 54 of the valve is only a small fraction of the width of a cooperating port in the valve. In practice, a movement of five to ten thousandths of an inch is found satisfactory. Following each pull of the electromagnet, a centering device 15 serves to bring the lever 16 back to its mid-position. There is, therefore, a consequent gradual movement of the motor piston in one direction. At the same time that these periodic impulses are delivered to the motor, one of the solenoids I08, llll becomes energized and delivers a steady pull to the fulcrum point 64 upon the lever 60 and tends to drag the valve piston to a fully-opened position. Whether or not it reaches fully-opened position depends upon the length of time that the contacts l3 and 2G, for example, remain closed and upon the setting of the dashpot H2 which delays this movement. As soon as the contacts are opened, both the vibratory force and the steady pull applied to the valve piston are reduced to zero, and the piston is returned to its neutral position, as shown in the drawing, by the action of the centering devices l5 and HM. This return movement is immediate and does not wait for the dashpotcontrolled bell crank ild to be pulled back to contact with a pin M8 by the spring H6.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. In a cyclically operated control system, a movable member, a motor for moving the member, a device for connecting the motor to a source of power, an operator-controlled means constructed and arranged to determine the direction and extent of movement of the member by control of said connecting device, and means for rapidly vibrating said connecting device many times during each cycle, said latter means being set in operation by'movement of the operator-controlled means.

2. In a cyclically operated control system, a hydraulic motor, a valve controlling said motor and having a neutral closed position, means for normally holding said valve in its neutral position, and means for periodically vibrating the valve through only a range both limits of which li at one side of its neutral position during a cycle of the control system to produce a gradual movement in the sense indicated by the position of the range with respect to the neutral position.

trol valve for said motor, electromagnetic means for recurrently moving said control valve in one 3. In a fluid-pressure system, a motor, a condirection away from a, neutral closed position intermittently to open the valve to send a series of impulses to the motor, and resilient means urging said control valve toward its neutral position after each movement.

4. In a fluid-pressure system, a, motor, a con.- trol valve for said motor, a pivoted armature connected to said valve, an electromagnet for turning said armature to open th valve, and operator-controlled means for delivering a pulsat ing current to said electromagnet.

5. In a. fluid-pressure system, .2: motor, a reversing valve for said motor, a pivoted armature connected to said valve and spring-biased to hold said valve in its neutral closed p0sitio.-r.., electromagnets operating said armature arranged respectively to open said valve in opposite directions, and means for delivering a pulsating current to one of said electromagnets, thereby to cause a smooth, gradual movement of the motor in thedesired corresponding direction.

6. In a fluid-pressure system, a. motor, a control valve for said motor having coacting valve members, resilient centering means for one valve member, means for imparting to the one valve member a series of rapidly repeated impulses in one direction away from its initial position tending to open said valve and then to release it, and means also connected to said valve member for imparting a steady force in the same direction as the series of impulses.

7. In a fluid-pressure system, a motor, a control valve for said motor having coacting valve members, spring-biased electromagnetically-operated means for delivering a. series of pulls intermittently to one of said members to open said valve slightly, and a delayed valve-operating device arranged to impart a steady opening pull to the same valve member.

8. In a fluid-pressure system, a motor, a control valve for said motor, a lever connected to said valve to move it, means for imparting a pulsating movement to said lever to open the valve intermittently, and additional means for imparting a steady pull to said lever to open the valve a progressively greater amount.

9. In a fluid-pressure system, a motor, a slide valve controlling said motor, a lever connected to said slide valve, means for vibrating said lever to open the valve intermittently, and means for moving the fulcrum of said lever to fully open the valve.

10. In a fluid-pressure system, a. motor, a slide valve for controlling 'said motor, a plurality of electromagnets each connected to said valve to move it in the same direction, means for supplying a pulsating current to said magnets, and means for smoothing out the current delivered to one of the magnets.

11. In a fluid-pressure system, a motor, a slidevalve mechanism controlling said motor, an electric solenoid mechanism connected to said slide valve, 2. spring mechanism tending to return said valve to closed position, a one-way dashpot mechanism loosely contacting the solenoid mechanism to delay the action of said solenoid, and a spr for restoring the dashpot mechanism when the solenoid becomes ineffective.

12. In a fluid-pressure system, a motor, a reversing control valve for said motor, a lever connected to said control valve, displaceable fulcrums at the opposite ends of said lever, springs returning said fulcrums to a predetermined position, means for imparting a vibratory force to said lever to move one end of it to open the valve valve to operate the motor in a direction corresponding to the direction of the range of movement imparted by the armature.

GEORGE T. HART, JR.

' REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Number Anderson Au 16, 1921 Number Number 8 Name Date Roucka Oct. 21, 1924 Sperry Nov. 8, 1932 Fischer Nov. 11, 1941 Wilson July 24, 1934 Donaldson Dec. 15, 1942 Wilde Jan. 6, 1942 Smith Feb. 8, 1944 Martineau May 26, 1914 Rouse Apr. 19, 1932 Warren Mar. 1'7, 1925 Hewlett Sept. 11, 1928 Overbeke July 30, 1940 Rosen Apr. 25, 1944 Bates Feb. 6, 1945 Hodgkinson Aug. 24, 1915 FOREIGN PATENTS Country Date France June 16, 1931 Great Britain Dec. 20, 1935 

